November 12, 2015
Chpt 5: Integumentary System
cutaneous membrane = integument = skin
largest organ in body
Integumentary system includes skin + accessory
organs: hair, nails, oil glands, sweat glands
Anatomy
2 layers to skin
1- epidermis: thin, outer layer
2- dermis: inner, thicker layer
hypodermis = subcutaneous layer: beneath skin
epidermis and dermis are firmly bound together
blister is sep of 2 layers, filled with water
November 12, 2015
Epidermis: composed of stratified squamous epith
even though this is the thinner layer, it is made up
of 5 layers
5 layers from innermost to outermost
1-stratum basale (germinativum)
innermost layer of cells, superior to dermis
most impt layer, cells rapidly undergo mitosis
these cells give rise to all other layers
new cells are produced at rate old cells are
sloughed off at the surface of skin
cells take 2-4 weeks to rise to surface
there are no blood vessels in epidermis, as
cells divide, they move upwards to more
superficial layers and then they die----->
due to no nutrients & O2
Langerhans cells are found in this layer
these are a type of WBC that phagocytize
any microbes found here
melanocytes are also found here
these are melanin-producing cells
the number of melanocytes is approx the
same in everyone, but the amount
of melanin produced is different
melanin protects skin against harmful UV
rays
melanin production is stimulated by sunlt,
melanocytes prod more melanin &
distribute to epidermal cells
November 12, 2015
Epidermis cont.
2-stratum spinosum: spiny-shaped cells
cells are changing from cuboidal shape of
str. basale and beginning to flatten out
3-stratum granulosum: 2-3 layers of flattened cells
this layer is active in keratinization
keratin: waterproof protein that hardens
cells and protects against water loss & gain
cells lose nuclei as they become keratinized
thus cells die in this layer, so epidermis
becomes a protective wall
4-stratum lucidum: very thin, transparent layer
cells are flattened, keratinized
2-3 layers of cells
November 12, 2015
Epidermis cont.
5-stratum corneum: outermost "horny" layer
composed of hard, flattened cells
as cells move fr. str.basale to str. corneum,
they flatten out, harden and die
this layer is really composed of dead cells
converted to a protective protein
cells are covered & surrounded by lipids also
these cells have only 20% water
as many as 25 layers of flattened cells
this layer is the first barrier against microbes
layer is constantly sloughed off to maintain
good wall of protection
November 12, 2015
Dermis - deep skin
made of dense irregular connective tissue
contains collagenous fibers - flexible but resistant
to overstretching
they protect skin from tearing
contains elastic fibers - allow movement of
underlying muscle & joints
also helps maintain skin tension
contains blood vessels
feed cells of dermis & stratum basale
contains sensory nerve fibers
touch, tissue damage (pain), press
November 12, 2015
Subcutaneous layer or hypodermis
"underneath the skin"
loose areolar connect tiss & adipose tiss
fat - E storage
insulation
padding against injury
Back to Epidermis
freckles - patches of melanin
albinism- lack of ability to prod melanin
no pigmt in skin, eyes, hair
carotene - another pigment in skin
gives orange-yellowish color
pink skin - due to blood
November 12, 2015
Accessory organs
hair- all over body except palms of hands, soles of
feet, lips, nipples
found in hair follicles
at base or root, living cells continually divide
hairs are nourished by dermal blood vessel
hair follicle is made of epidermal tissue
as hair grows up & out of follicle, cells become
keratinized & die
root-the part in follicle that is living
shaft-hair extending beyond skin, dead
root cells are fed by blood vessels at root,
as cells move away fr. root they die
lifespan of eyelashes 3-4 mo.
lifespan of scalp hair - 3-4 years
each hair has sebaceous gland attached, these
secrete oil or sebum that keeps hair & skin
soft & pliable
each hair has involuntary musc attached to follicle
called arrector pili musc
when it contracts: hair stands on end, you get
"goosebumps"
alopecia - hair loss
this can be genetic-male pattern baldness
or it can be a sudden loss-chemotherapy,
radiation
November 12, 2015
Access org: nails
nail root (bed) - living epidermal tiss
cells divide, move out, become keratinized
function-protection
Glands: sweat, sebaceous, mammary, ceruminous
1-sweat glands - sudoriferous glands
tubular, coiled gland
2 types: one opens into hair follicles in anus,
groin & armpits; other opens directly
onto skin
both have excretory function: secrete water,
salts, urea
helps lower body temp
glands in groin & armpit also produce sex
pheromones - attractant
also active under stress
November 12, 2015
Glands cont.
2-ceruminous glands: modified sweat glands in
ears, produce cerumen (wax) for lubrication,
protection
3-mammary glands: modified sweat glands in
breast, prod milk under hormonal influence
4-sebaceous glands: produce sebum, oil
lubricates hair & skin
attached to each hair follicle in scalp & skin
also helps waterproof skin
acne-inflammation of sebaceous glands
hormonal changes cause them to be more
active